You were 100% incorrect about being fully vaccinated requiring a quarantine no matter what, a test is not difficult to achieve within the 48 hour time limit for a PCR test prior to travel, especially with many urgent care clinics offering 1-2 hour PCR test results, or less than 24 hours ahead for proctored antigen testing.
https://www.philippineairlines.com/en/ph/home/covid-19/arrivingintheph
What may be more difficult is to get a return PCR or antigen test within the 24 hour time limit from departure for the USA if they reinstate testing for everyone entering the USA, but getting a test to go to the Philippines is quick and easy.
Only if one wished to skip the testing entirely on the way to the Philippines does one need to be both vaccinated and boosted, otherwise a fully vaccinated passenger only requires a test to avoid quarantine.
If you are a foreign national who is unvaccinated, partially vaccinated or unverified you won't be allowed into the Philippines, but they haven't changed the definition of fully vaccinated to avoid quarantine, only gave the option to skip testing if having had at least one additional booster on top of your primary series of vaccination.